The present invention relates to digital signal recording and reproducing apparatus which is particularly useful in commercial applications.
Known digital video tape recorders (digital VTR's) designed for commercial applications digitize and record video and audio signals, as main and sub information signals, respectively, in correspondingly different areas in slant tracks formed sequentially on a video tape. The known digital VTR is provided with an after-recording mode of operation in which only an audio signal and a sub code signal are again recorded.
FIG. 1 of the accompanying drawings illustrates the format of one of a plurality of slant tracks 20 formed on a video tape by the digital VTR. As shown in FIG. 1, the various signals are recorded sequentially in the track 20 by a recording head (not shown for purposes of simplicity and clarity) scanning the track beginning at an initial track scan position 22 and proceeding to a final track scan position 24 thereof. Accordingly, as the recording head scans the track 20, from the initial track scan position 22, a first automatic track following (ATF) signal recording area AT1 is formed in which a first ATF signal for use in tracking adjustment is recorded. In sequence thereafter, a first audio signal recording area AU1 is formed in the track 20 wherein a first audio signal is recorded (also referred to as a first sub information signal). Subsequently to the formation of the recording area AU1, a second audio signal recording area AU2 is formed in which a second audio signal is recorded (also referred to as a second sub information signal). Following the formation of the recording area AU2, a video signal recording area VI is formed in which the video signal is recorded (also referred to as a main information signal). Following the formation of the area VI, a sub code signal recording area SC is formed in which a sub code signal is recorded (also referred to as a third sub information signal). Finally, adjacent the final scan position 24, a second ATF signal recording area AT2 is formed in which a second ATF signal is recorded for tracking adjustment purposes.
It is often seen that the track angle and the angle at which the head scans the recording tracks do not coincide because of a lack of compatibility between the digital VTR and other apparatus. In that case, the automatic tracking control function is carried out with the use of the first and second ATF signals reproduced respectively from the ATF signal recording areas AT1 and AT2 of each of the tracks. In operation, the respective tracking error signals are detected from the reproduced ATF signals, and then automatic tracking control is carried out so that the tracking error signals are both minimized. Consequently, the automatic tracking function is carried out so that the scanning locus of the head (indicated by the dash line x in FIG. 1) coincides with the track 20 at the center of the tape.
If the above described automatic tracking-control technique is employed, then the video signal is reproduced satisfactorily. However, in the after-recording mode of the digital VTR in which only an audio signal and a sub code signal are recorded, for example, the track 20 and the head scanning locus do not coincide either in the audio signal recording area or in the sub code signal recording area. Consequently, it may be that after-recording cannot be carried out satisfactorily with the use of the above described automatic tracking control technique.